Sports Medicine Research: In the Lab & In the Field: Near Point Convergence Is Worsened with Intense Subconcussive Impacts (Sports Med Res)


Wednesday, July 6, 2016

Near Point Convergence Is Worsened with Intense Subconcussive Impacts

Association of Football Subconcussive Head Impacts With Ocular Near Point of Convergence

Kawata K, Rubin LH, Lee JH, Sim T, Takahagi M, Szwanki V, Bellamy A, Darvish K, Assari S, Henderer JD, Tierney R, Langford D. JAMA Ophthalmol. 2016; ahead of print

Take Home Message: Football players with significant subconcussive impacts had impaired near point convergence before and after full contact practices compared with baseline scores. Football players with less intense head impacts showed no changes over time. Near point convergence may be a useful clinical tool to implement in sports at risk for subconcussive impacts. 

Subconcussive head impacts occur more frequently than concussive blows and may cause long-term neurological deficits. However, there are no clinical tools to detect the neurological consequences of subconcussive head impacts within one sport season. Therefore, the authors assessed whether repetitive subconcussive head impacts during preseason collegiate football is associated with changes in near point convergence (a measure of the closest point someone can follow an object coming towards their face). The authors collected head impact kinematic data, near point convergence measurements, and SCAT3 sign and symptom scores during preseason physical examination (June 2015), before and after 1 noncontact and 4 full-contact football training camp practices (3 to 4 days in between), and 3 weeks after the final game. Based on the 5-practice kinematic impact data the authors categorized the athletes into a low impact group (7 athletes) and a high impact group (22 athletes). To measure near point convergence the athlete was seated with the near point convergence ruler placed on the athlete’s upper lip and they focused on a reduced size Snellen chart as it moved toward their face. The near point convergence measurement was taken when the athlete said that the chart went double or the tester observed eye misalignment. There were no differences between impact groups and their demographic data (age, BMI, years of experience, concussion history). Both groups had similar near point convergence at baseline. However, the higher-impact group had greater worsening over time that resolved by the post-season time point. Conversely, the lower-impact group had no change in near point convergence overtime. There was no change in sign and symptom scores between groups or from preseason to post season.

Overall, the authors found that repetitive subconcussive head impacts might compromise near point convergence function without athletes reporting changes in symptoms. However, this only occurred in the high impact group, which was exposed to a greater number and magnitude of impacts. The decline started with the pads-on practices, which is not surprising because this is when contact practices begin. It was alarming to see the decline worsen across the contact practices. Fortunately, these players showed improved near point convergence after a 3-week rest period after the season. This may suggest that ocular-motor function could reflect subclinical brain damage and recovery. It will be interesting to see if future studies confirm these findings, especially among studies that perform baseline testing closer to the start of football training camp practices. Healthcare professionals, athletes, and parents should be aware of the potential harm to the ocular-motor system from subconcussive blows. Though further research is necessary to investigate the clinical relevance, the authors demonstrate that adding a near point convergence measurement to a baseline concussion protocol could be beneficial in assessing subclinical concussions.

Questions for Discussion: Should we be monitoring head impacts? Are you using near point convergence in your concussion protocol? Do you believe these subclinical concussions/subconcussive impacts will cause long-term effects?

Written by: Jane McDevitt, PhD
Reviewed by: Jeff Driban

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Haley said...

I think monitoring every head impact for every athlete is unrealistic...especially for health care providers who cover multiple teams at a time. I believe that a baseline near point convergence test can be clinically useful when assessing for a concussion and can be used in the diagnostic process. In terms of future research, I would like to see what these athletes in the high impact group look at 6 months, 1 year, and 5 years post-season in order to determine if these impacts have any long-term effects on individuals.

Jane McDevitt said...

I agree it would not be feasible to check an athlete's convergence after every head impact. However, I think that if you are using convergence as one of your concussion assessments in season, and your athlete participates in a position that he/she may have had several high head impacts I would error on the side of caution and be more conservative with the near point convergence reading. This study found that 3 weeks after no head impacts the athlete's convergence measurement went back to baseline levels. Though, you bring up a good point on what happens to the athletes that play year round. They may not get a break and it may be additive over the years. That would be an interesting study.

Tyler Keith said...

I think this article brings up a few points that I have thought about in my clinical experience. To begin, I have never monitored near point convergence or utilized it in concussion protocol, but I am beginning to think it may play a large role, especially in recovery from concussion. In working with a hockey team this past year, we found that those who had disturbances with their ocular-motor function (as found by an ocular-motor specialist), had increased recovery times from concussion. We began to believe that these ocular-motor functional impairments caused increased symptom longevity, and the quicker you address the impairments, the quicker you may help the symptoms go away. Therefore, I do believe it will be important to begin monitoring ocular-motor function via baseline testing (near-point convergence being a good example of this), as retesting athletes two-three days post concussion should help identify those with functional impairments.

At this point in time in concussion research, I think it is difficult to identify whether subconcussive hits will cause long-term effects. You could attempt to monitor the amount of subconcussive hits they receive each year or each season, but even then it begins to become difficult categorizing what is or isn't a subconcussive hit, as well as their accuracy in reporting them outside of sport. The fact that the athletes returned to normal with three weeks rest is interesting, but I begin to wonder how much learning would impact that process. Athletes may be able to get three weeks of rest after the season during the school year, but they do not receive any cognitive rest during this time.

Jane McDevitt said...

I think it is great you have the ability to work with an ocular-motor specialist. I have had similar successes when employing ocular therapy with athletes who are having persistent concussion s/s. I agree it would be very difficult to identify subconcussive hits will cause long term effect. You need to have the tools to even consider it. Within this study and other studies looking at the cumulative effects of subconcussive blows they have helmet accelerometers measure the g forces and they can categorize and identify what constitutes a sub concussive blow. It is very interesting work; however, as you pointed out is not clinically relevant at this time.

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